Early age at menarche is associated with an increased risk of breast cancer. Among determinants of age at menarche, diet appears to be of great importance because malnutrition can delay the adolescent growth spurt and menarche, overnutrition as indicated by obesity is associated with decreased age at menarche, and long-term changes in diet appear to parallel the secular trend to earlier menarche that has occurred since 1850. The objective of this 5-year study is to determine the association of specific dietary factors with age at menarche and with anthropometric measurements which indicate growth. The methodology will involve the collection of dietary data and anthropometric measurements and the determination of the age at menarche prospectively in 9-13 year old girls. The dietary data will consist of 24-hr recalls and food frequency questionnaires administered to the subjects at school at unannounced periods at six-month intervals; the anthropometric measurements will be made at the same time. The occurrence of menarche will be indicated by the mother's response to a questionnaire administered at six-month intervals which will also indicate the girl's food frequency usage. Dietary variation in the study population is achieved by including a school population of Seventh-Day Adventist girls to represent nonusers or light users of meat, poultry and fish and a group of girls from public school to represent the standard American diet with heavy use of meat, poultry and fish. The study will provide specific data for dietary factors which may be predictors for age at menarche such as gram estimates of the average weekday intake of specific nutrients such as total fat, animal protein, etc.; frequency of use of specific food items such as milk, eggs, etc., as reported by the subject and by her mother, as well as other data reported by the mother. The analysis of this data will permit the determination of the degree of association of specific food items and/or specific nutrients with age at menarche.